How Do I Inspect A Standard Cobra Lower End? 1987 2.3L

The lower end is off of a 1987 Standard Cobra, 2.3L Ford, and separated from the upper unit.

With the unit on a bench, I push the shift rod down while rotating the prop CW and it shifts into what I think is forward. I continue to rotate the prop and all is smooth.

I then move the rod to neutral and spin the prop. All is smooth and quiet.

I then move the rod all the way up into what I think is reverse. Spinning the prop CCW I hear a muted gear noise. Spinning it CW it's louder.

Maybe I should be turning the driveshaft instead of the prop for this check?

Question: Is it normal for the gears to make some noise in reverse? (Like an automobile reverse makes noise (standard trans).)

Re: How Do I Inspect A Standard Cobra Lower End?

You have the thing off, so go ahead and put new bearings and clutch parts in. Hope you don't find chewed up bevel gears.

Re: How Do I Inspect A Standard Cobra Lower End?

First of all, I'm not going to spend a dime on this outdrive until I understand what is going on.

When I tested the outdrive on the muffs and later at the lake, it was smooth and quiet in forward and reverse. No vibration at all. It shifted flawlessly, too.

Now, with the unit on the bench, when I spin the prop by hand, I can hear some noise. I need to find out the how to analyse the condition of the gears and bearings without taking it apart.

I read thru the outdrive section of the manual, and did not find an answer to my question.

One thing I did find out, reading the manual, the OMC Cobra outdrive is quite complicated in assembly and requires many special tools. But perhaps a VP mechanic has some of those.

Re: How Do I Inspect A Standard Cobra Lower End?

DavidW2009 said:

First of all, I'm not going to spend a dime on this outdrive until I understand what is going on.

Click to expand...

Well, lets not kid ourselves here. You are already in hip deep my friend considering your time and the parts you will have to buy just to get it all back together. I hate to come off as snide, but I must ask why, if you have already gone to the trouble of disassembling the drive, would you simply slap it all back together and hope for the best? You are two thirds into the thing and at this point it would be a good idea to go on and finish the tear down and replace the bearings at the very least as well as the zinc on the carrier, just as a preventive measure.
I don't have my manual in front of me, but I don't recall seeing anything in the way of special tools that can't be accomplished with home brew expedients. The tools make it easier by a mile but not worth the expense if you aren't doing these things as a full time business. As a secondary strategy you could take it to a place that does have the tools and have them take it apart for you.

Re: How Do I Inspect A Standard Cobra Lower End?

He hasn't disassembled it as far as I can tell.

Only way to evaluate gears is via disassembly.

Re: How Do I Inspect A Standard Cobra Lower End?

Thanks for the replies.

I do plan on spending some money on this, but I just want to understand what's going on before I take it apart, and if it is necessary to take it apart.

The outdrive ran well on the lake. No water in the oil. Ran smooth and quiet.

I have separate the upper and lower units (not disassembled the lower end yet) for several reasons:

1. Just curious
2. Remove the wasp nests
3. Check the intake water passages
4. Check the drive o-rings and seal

I'm trying to determine if it's possible to detect a flaw in the lower end by rotating it by hand. I use to rebuild differentials and got to where I could 'feel' a bad bearing or detect bad tooth engagement.

But this marine stuff is a different animal with different parameters.

Re: How Do I Inspect A Standard Cobra Lower End?

DavidW2009 said:

I use to rebuild differentials and got to where I could 'feel' a bad bearing or detect bad tooth engagement.

Click to expand...

sure, but if you didn't feel it ... did you assume everything inside was mint?

Re: How Do I Inspect A Standard Cobra Lower End?

"... did you assume everything inside was mint?"

If it wasn't low on oil or leaking, yes. I used that criteria when buying old cars on the cheap.

Re: How Do I Inspect A Standard Cobra Lower End?

well, then use that criteria for buying old drives on the cheap. gears are gears and bearings are bearings.
a differential and an outdrive are similar in that regard.

Re: How Do I Inspect A Standard Cobra Lower End?

On my lunch break, I relooked at the the lower end. I inserted the drive shaft into the lower end and (looking from the top down) rotated it CW and checked for noise in forward and reverse. There was none.

I could feel no bad bearings or detectable backlash in the hypoid gears. The backlash is a bit harder to analyse because of the clutch dog design and the rotational free-play in the dogs.

I realise now that rotating the prop to check for noise (while in one gear or the other) is not the way to do it. Except in neutral, only the prop shaft carrier bearings can be checked by rotating the prop.

Also, with a torque wrench, I'm going to check to see how much torque it takes to rotate the inputs on the upper and lower units. I noticed it took about twice the torque to rotate the upper as the lower when doing it by hand. The lower unit really did turn very easily from the vertical driveshaft.

Although you can get some of it's condition by shifting it into fwd and rev when rotating the driveshaft, you can't tell if the dog clutch is going to be able to stay in gear under load and that's the thing that causes most lower unit rebilds, unless it was run low on oil in which case the whole thing would have to be gone through. Running it on the boat is the only way to tell if the dog clutch is good....

http://www.hastings.org/~stuart/cobra/ Read this before you go any further! These adjustments are critical. Also look at S.E.I. as a replacment outdrive, will cost around $1400 to $2000 to swap/. I am not an expert, just a 2.3 boat owner/. I have gone thru three of these 2.3 outdrives, one that came with the boat, and two used ones. You get what you pay for (mine were cheap)

If everything was fine on the muffs and in the lake and it was smooth and shifted good, Why did you ever take it appart ???

Iouc,
I did run it on the lake twice and the outdrive worked fine, smooth, shifted slick as could be, no noises while under way.
Had no trouble with it coming out of gear under way.


floatin Radio,
I've read the stuart article and refer to it from time to time.


Boobie,
See my post #6.

After work today, I fooled around with the upper and lower units and realised I made a categorical error in the torque required for the upper unit. I forgot I still had the impeller on. Removed the impeller and torque required went down quite a bit. Duh.

Having the upper and lower units separated have given me an opportunity to inspect all the passages for debris and water flow. Found no trash or anything. Water flowed freely thru the upper unit and the same for the lower unit. If there is a bottle neck in the flow it's at the intake screen where raw water is taken in. Also, upon back flushing the lower unit, I noticed the water was kind of foaming as it exited the intake screen. I hope it doesn't do that in the other direction while running on the lake....?

I have read (on another forum) more than a few comments pertaining to problems with OMC Cobra's engine overheating at idle, but working fine at speed. I wonder if there may be some quirk that under the right conditions, a Cobra does not intake enough water at idle????